Conventionally, for the sake of power-saving in an electronic device such as a personal computer and the like, a sub power source type electronic device is known in which a main voltage is supplied from a main power source during operation of the electronic device. The main power source is turned off and a small amount of sub voltage is supplied by a sub power source when the electronic device does not constantly operate for a certain period of time (JP Patent No. 2,997,584).
However, in the above conventional electronic device with the sub power source type power source for power-saving, there is a problem that a power circuit becomes complicated in a case where an auto power-off function is added that automatically switches a current-application state to the apparatus. Therefore, it is desired to add the auto power-off function with a simple configuration to such an electronic device with the sub power source and the main power source.